1. Field of the Invention
The present invention relates to a chip package structure. More particularly, the present invention relates to a chip package structure with a lead frame.
2. Description of Related Art
The production of integrated circuit (IC) devices is mainly divided into three stages including IC design, IC process and IC package.
In the stage of IC package, a bare chip is obtained via wafer production, circuit design, photomask formation and wafer sawing. Each bare chip obtained by sawing the wafer is electrically connected to a substrate via bonding pads formed on the chip. A molding compound then encapsulates the bare chip to protect it from being adversely affected by external moisture and being polluted by dusts. Moreover, an electric interconnect between the bare chip and an external circuit is maintained. A chip package structure is thus constructed.
FIGS. 1A and 1B are respectively a top view and a cross-sectional view of a conventional chip package structure. A chip package 100 includes a lead frame 110, a chip 120, a plurality of bonding wires 130, and a molding compound 140. The lead frame 110 includes a die pad 112 and a plurality of leads 114 surrounding the die pad 112.
The chip 120 includes an active surface 122 and a back surface 124 opposite to the active surface. The chip 120 is disposed on the die pad 112, and the back surface 124 of the chip 120 faces the die pad 112. The active surface 122 includes a plurality of contacts 126, and the bonding wires 130 electrically connects the contacts 126 to the leads 114. The molding compound 140 encapsulates the die pad 112, the leads 114, the chip 120, and the bonding wires 130, so as to prevent the chip 120 from being adversely affected by external moisture, heat, and noises. Further, the bonding wires 130 can also be protected from external damage.
In a conventional chip packaging process, the molding compound is formed by providing a semi-solid molding compound material e.g. epoxy resin at high temperature. Next, the molding compound material is molded and cooled, such that the molding compound is formed on the lead frame and encapsulates the chip. However, the impact arisen from an injection of the molding compound material may force the leads to wobble or shift, and thereby the adjacent leads are likely to be electrically connected to each other. Moreover, the production yield of the chip package structure is reduced as well.